Connection oriented point-to-point communication links, such as a Layer 2 Tunneling Protocol (L2TP) tunnel, are an increasingly common feature of network infrastructures. Tunnels are prearranged connections established by agreement between internet service providers (ISPs). See Request for Comment (RFC) 2661 and Layer Two Tunnelling Protocol (L2TP), A. Valencia, et al., draft-ietf-pppext-12tp-16.txt, June 1999, herein incorporated by reference, available from the Internet Engineering Task Force (IETF) at www.ietf.org for more information. FIG. 1 shows an architecture 10 that illustrates two L2TP tunnels 56 and 58 from tunnel initiators 30 and 40, respectively, established through a public IP network 70 to a tunnel endpoint server 50.
An L2TP tunnel typically provides a conduit for communications between client devices served by the tunnel initiators and a server device served by tunnel endpoint 50. Typically, a single tunnel slot provides the communication link between a client and server.
When a client device establishes a dial-up connection with a tunnel initiator (TI) 30 or 40, then the TI typically recognizes the client device as a tunnel client by means of an authentication protocol, such as RADIUS, see Request For Comment (RFC) 2138, herein incorporated by reference, or by other means for identifying the client, such as through the use of a mobile identification number (MIN) in mobile applications or, for protocols not directed toward mobile applications, the use of a Dial-up Number Information Service (DNIS) or Automatic Number identification (ANI). The authentication process can be adapted to provide an address for a tunnel endpoint device for the client. Alternatively, the client device itself may provide the tunnel endpoint address. In still another approach, each TI may have a pre-constructed table containing entries that associate a client device identifiers with a tunnel endpoint address value. Independent of how the tunnel endpoint address is obtained, the tunnel initiator will establish a tunnel connection to the tunnel endpoint device.
Tunnel endpoint devices are typically stand-alone devices that operate independently of other tunnel endpoints. As a result, the tunnel endpoint devices are difficult to scale in order to cope with high levels of traffic to a server device connected to the tunnel endpoint device. In addition, with a single tunnel endpoint device serving a given server device, failure of the tunnel endpoint device can block all traffic to the server.
Thus, the need remains for a method for providing multiple tunnel endpoint devices that can serve a single server device.